Finding the right clock key


Here we have clock keys in all the sizes available. We get many calls asking what key their clock takes and over the phone it is difficult to say what key size is needed.

Best to read the below text on how to use the clock keys chart and get the correct sized key to wind your clock.

What can be said is most larger German movements take a number 8 key.

So if your clock movement is made in Germany, is 5 x 5 square or 6 x 9, it will take a number 8 usually. If the clock movement is made in Germany and it's round or a small rectangle it's usually number 4.

If you have a 31 day clock, or a Korean clock, or a commonly produced early American time strike movement, then it's usually number 7. However, if you want to be sure with all this then use the below chart.

1 CM = 10 MM
25.4 MM (2.54 CM) = 1 inch
Brass Clock Key

Brass Single End Clock Key


Available in many sizes, this is the most popular choice on this page.

Please use the key chart to find out what key you would need.

Item #CK4

Using the key size chart


To get the key you need, measure the shaft the key is to go on to, then use this chart to get the key size # you need.

Please do not call asking what key your clock needs, as you will be told it would still have to be measured.

Again, you are measuring the shaft that the key goes onto in MM and then using the below chart.

    Shaft width / Key # needed
  • 1.75mm = 000 Key
  • 2.0mm = 00 Key
  • 2.25mm = 0 Key
  • 2.5mm = 1 Key
  • 2.75mm = 2 Key
  • 3.0mm = 3 Key
  • 3.25mm = 4 Key
  • 3.5mm = 5 Key
  • 3.75mm = 6 Key
    Shaft width / Key # needed
  • 4.0mm = 7 Key
  • 4.25mm = 8 Key
  • 4.5mm = 9 Key
  • 4.75mm = 10 Key
  • 5.00mm = 11 Key
  • 5.25mm = 12 Key
  • 5.5mm = 13 Key
  • 5.75mm = 14 Key
  • 6.0mm = 15 Key

13 Clock keys 13 Clock keys

The most common sizes in a assortment of single and double ended keys

Item #CK1-- $35

Double End Clock Keys Double End

Four most popular double end clock keys. There is always much confusion for people to get the proper double end key, so we offer this set of 4 keys most frequently used. These have the Small end for regulating some clocks as well as the end to wind.

Item #CK2-- $19

Schatz 400 Day Clock Key Schatz 400 Day

#3 size for lantern style 400 day clocks

Item #CK3-- $12

Alarm Clock Keys Alarm Keys

A dozen assorted small keys for alarm style wind up clocks. These are for clocks such as big ben or baby ben styles as well as others.

Item #CK5-- $13


Grandfather Clock Key Crank Grandfather Crank

Available in 5 sizes. This crank is brass with a wood handle.

Item #CK6-- $19

OGee Clock Key OGee Clock Key

Available in 0 to 13. This crank is usually used for the OGee mantle clock.

Item #CK7

5 Prong Clock Key Set 5 Prong Key Set x2

These two 5 prong clock keys will cover just about every clock winder.

Item #CK8 -- $19

GF Clock Crank GF Clock Crank #8

#8 Crank -fits just about all modern clocks such as Hermle, and Kieninger.

Item #CK9-- $19


French Style Clock Key French Style

Available in all sizes. Please use the key size chart on the top of the page.

Item #CK10

Clock Door Key Door Key

This door key fits most modern clocks such as Howard Miller and others.

Item #CK11-- $9

Hermle Clock Key Hermle Key

#8 Key -fits most Large Hermle model clocks, #4 Key -fits most Small Hermle model clocks.

Item #CK12

Clock Key Gauge Clock Key Gauge

If you have many keys and do not know what size they are, this gauge will help. Just put the key on the correct post and it will tell you what size it is.

Item #CK13-- $21

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F / S at 12 O’clock key note

If you see an F / S or an A / R around the 12 o’clock area of the clock dial, this is called a regulator. So for F / S this means fast or slow, and the A / R would represent advance or retard. So turning the arbor toward F will make the clocks time run faster and the opposite direction for slow. To turn this you would use the small end of your clock key. If the key has been lost at one point then someone could have replaced the key with a single end key instead of double. The double end key is what you would need instead, one for the winding up the clock and the other side for the F / S regulation. There are many sizes and combinations for the double end key and it may be tricky to get the right size. So you may just want to get the 4 pack of double end keys we offer. This is the top 4 most common double end clock keys that are used so the odds are with you that you will get the correct key with both sides fitting your clock movement. We offer this at the following link

F / S at 12 O’clock Continued

Now sometimes a person will be tired of using the fast / slow regulation, or the parts in the back of the clock movement, such as the pendulum hanging wire, has been replaced with one too short. If this is too short then you may need to adjust the fast / slow beyond what the regulator is designed to adjust. If this is the situation you may just want to get an adjustable bob to regulate the clock instead. If you get the adjustable bob instead you do not need a double end key. You only need to adjust the nut on the bottom of the pendulum bob as to raise the bob to speed up the clock time or the opposite to slow the clocks time down. So if you choose to get the adjustable bob, please see it displayed at the following link. The adjustable pendulum bob comes in three sizes, or bob diameters. Usually the middle sized bob or the smaller bob is fine for most clocks.